Polyamine effects on protein disulfide isomerase expression and implications for hypersalinity stress in the marine alga Ulva lactuca Linnaeus1

Authors

  • Lu-Chuan Li,

    1. Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
    Current affiliation:
    1. Teacher in the Computer Science Department, Shu-Te Home Economics and Commercial High School, Kaohsiung, Taiwan
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  • Yuan-Ting Hsu,

    1. Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University, Kaohsiung, Taiwan
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  • Hsueh-Ling Chang,

    1. Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan
    2. Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
    3. The Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan
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  • Tzure-Meng Wu,

    1. Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan
    Current affiliation:
    1. Postdoctoral Fellow in the Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
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  • Ming-Shiuan Sung,

    1. Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan
    Current affiliation:
    1. Joint Doctoral Program in Marine Biotechnology between National Sun Yat-sen University and Academia Sinica, Taiwan
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  • Chung-Lung Cho,

    1. Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
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  • Tse-Min Lee

    Corresponding author
    1. Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University, Kaohsiung, Taiwan
    2. Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan
    3. Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
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  • Hsueh-Ling Chang, Yuan-Ting Hsu and Lu-Chuan Li contributed equally to this work.
  • Chung-Lung Cho and Tse-Min Lee are co-corresponding authors.

Abstract

Full-length protein disulfide isomerase (UfPDI) cDNA was cloned from the intertidal macroalga Ulva lactuca Linnaeus. Modulation of UfPDI expression by stresses and polyamines (PA) was studied. UfPDI transcription and enzyme activity were increased by hypersalinity (90) or high light illumination (1,200 μmol photons · m−2 · s−1), decreased by the addition of 100 μM CuSO4. An exposure to a salinity of 90 decreased PA contents. Treating with PA biosynthetic inhibitors, D-arginine (D-Arg) or α-methyl ornithine (α-MO), led to a further decrease and also inhibited UfPDI expression and recovery of the growth rate. These results suggest that PAs are required to activate UfPDI expression with hypersalinity, even PA contents are decreased at a salinity of 90. The induction of UfPDI expression by hypersalinity of 90 and tolerance to hypersalinity could be enhanced if internal PA contents rise. Sung et al. (2011b) showed that PA contents could be increased by pretreating with putrescine (Put, 1 mM), spermidine (Spd, 1 mM), or spermine (Spm, 1 mM) at a salinity of 30. Therefore, PA pretreatment effect on UfPDI expression was examined. Pretreatment with Spd and Spm, but not with Put, enhanced UfPDI expression after transferred to a salinity of 90 and restored the growth rate. In conclusion, induction of UfPDI expression by Spd or Spm before exposure to hypersaline conditions and continuous up-regulation after hypersalinity exposure are required for the acquisition of hypersalinity tolerance in the intertidal green macroalga Ulactuca.

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